import math
import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n = int(input())
    s = input()
    ans = 0
    for i in range(n):
        if s[i] == 'U':
            for k in range(i+2, n, 2):
                if s[k] == 'G' and s[(i+k)//2] == 'M':
                    ans += 1
    print(ans)


if __name__ == '__main__':
    main()